Optimizing Underground

Subsurface water systems can boost yields, carry nutrients

Nebraska farmer Don Anthony started using subsurface drip irrigation (SDI) in 2006 on sections of his 1,200-acre corn and soybean farm in the Central Platte Valley. He began with a parcel of flat land that had a power line running diagonally through it.

Anthony had always used a center-pivot system, but a 1997 federal agreement affecting his state requires field corners untouched by pivots to be watered as well. Failing to irrigate those areas would result in the loss of their irrigated status, meaning they could never be irrigated again.

Since 2005, Anthony has added 250 to 300 acres of SDI, which delivers water to crop roots through a series of pipes and nozzles normally buried 10" to 14" below the surface. This year, one 80-acre section of corn—irrigated with 15" of water throughout the course of the growing season—yielded 188 bu. per acre.

"My experience in the past seven years with the pivot here versus drip across the road is that I’ll put on about two-thirds to three-fourths the amount of water with drip as I do with pivot and get the same yield," Anthony says.

He’s not alone. The subsurface irrigation method, first adopted in the U.S. for vegetables, fruits and nuts, is supplementing and even replacing center-pivot systems for field crops. Representatives of three of the top SDI businesses—Netafim, the Toro Company and John Deere—say the system is attractive to farmers worldwide because of its potential to save water, boost yields and reduce ferti-lizer runoff.

Netafim is the world’s largest manufacturer of microirrigation equipment, including subsurface drip components. Michael Dowgert, Netafim USA communications director, attributes the increased interest in subsurface irrigation to GPS development.
"Now you are able to find the dripper lines," Dowgert says. Subsurface irrigation has been in use since the 1970s, but its use with GPS started in the late 1990s.

Cotton tops the list of U.S. field crops most often used with subsurface. In the West Texas area, Dowgert says, close to half a million acres receive belowground irrigation. Corn ranks second, and SDI is being explored in states such as Nebraska, around the Ogallala Aquifer, where water scarcity is a key concern.

Just a few years ago, Netafim installed about 400 acres of subsurface systems in alfalfa, Dowgert says. This year, the company expects to install more than 4,000 acres for alfalfa alone.

While alfalfa often is flood-irrigated, using subsurface can remove stress on the plant and result in "fairly significant yield increases," Dowgert says. Farmers can even irrigate the crop while harvesting it.

Interest grows. Hubert Frerich opened Eco-Drip Irrigation in Garden City, Texas, in the early 1980s after successfully irrigating his watermelon and cotton crops with a subsurface system. No high-producing wells existed in the area, so limited access to water made subsurface an efficient alternative, says Craig Hoelscher, who now co-owns the company along with three of Frerich’s children.

"It helps make every drop count," notes Hoelscher, who adds that the system is also used to spoon-feed crops with fertilizer. Eco-Drip has installed as many subsurface acres in the past 10 years as it did in its first 20, totaling 200,000 acres. The company is getting more questions about subsurface systems and seeing a small pickup in demand across the central U.S.

Some farmers are still using systems that were installed more than 25 years ago, Hoelscher says. In 2009, he notes, researchers at Kansas State University found that emitters in a 20-year-old subsurface system were providing more than 90% of the water flow they originally offered. Fewer than 2% of Eco-Drip’s subsurface systems stop working, he says, and those that do often fail because of poor maintenance.

Technological advances will only make it easier to install and maintain subsurface systems.

"Right now it’s simple, but it’s going to get even more simple," says Nir Aloni, chief agronomist for John Deere Water. He says adoption of SDI worldwide depends on four factors: climate, crop type, capital availability and equipment.

Farmers in northwest China, for example, have quickly adopted SDI for their corn and cotton crops, as it fits very well with their crop rotation and climate. Meanwhile, farmers in Southeast Asia might install drip tape that lasts for just a year in order to capitalize on water conservation benefits, and then install a longer-lasting system when money is available.

Farmers often purchase SDI equipment for 40-, 80- or 160-acre blocks or irregularly shaped fields, says Inge Bisconer, technical marketing and sales manager for the Toro Company’s microirrigation business. The company offers an extensive line of products, including microirrigation emission devices, pipelines, valves, controllers and filters for use in surface and subsurface crop applications.

Toro has developed computer design assist software, known as AquaFlow 3.0, that allows farmers to build a virtual drip system to maximize water use and optimize maintenance. An online tool called Payback Wizard from Toro allows farmers to plug in five pieces of information to determine how long it will take for them to pay for their subsurface system.

How it works. To install the system, a toolbar fitted with coils of drip tape is mounted on a tractor, which places the tape below-ground using shanks. The tape contains emitters that release water. Single rows of drip tape can be as long as a mile, Bisconer says, but are typically a quarter- or half-mile long. The tape can remain functional underground for up to 20 years.

Trenches are dug to accommodate larger pipes, which are connected to the mainline. The mainline, in turn, is hooked up to the filter and pump station. After the parts are connected, the system is flushed and pressure-tested before the trenches are filled and pipes are buried.

Water used in subsurface systems generally flows from a reservoir or well, Bisconer says.

It is then pumped through filters that clean the liquid so the laterals don’t get clogged. Fertilizers might also be injected, along with chemicals that help maintain pipes.

Factors to consider. Subsurface irrigation isn’t for every acre. Square fields, for example, might be better served with a center-pivot system paired with SDI at the corners. Farmers in states with ample rainfall might not see the economic benefits realized by those in more arid states.
Cost should also be considered.

Installing a drip-line system generally costs about $1,400 per acre, Netafim’s Dowgert says. That’s roughly twice the cost of installing a center-pivot system.

Gophers pose a major problem to subsurface systems. Infestations can reduce alfalfa yields up to 50%, Dowgert says, and fields already populated by gophers are not ideal candidates for SDI. In the event that the creatures create problems after subsurface is installed, farmers can try using a product such as Netafim’s Protect-T, a rodent repellent that is piped through the drip system.

Maintenance is a mixed bag. While winterization is required after harvest to flush pipes and reduce buildup from hard water, experts say a variety of automation options lets farmers control how much time they spend turning valves by hand.

Anthony, the Nebraska farmer, thinks SDI will help him maintain a healthy standard of living: The 62-year-old says he’s getting to the point where his body can’t handle the intensive labor required for the alternatives such as flood irrigation.

"This is one of the things that will probably extend my farming career," Anthony says.